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California’s 'Salad Bowl' Recharges Depleted Aquifer

A multi-partner water recycling project is helping Monterey, Calif., stabilize and replenish its dwindling groundwater supply. The project could serve as a model for shrinking aquifers in other regions of the country.

Advanced Water Purification Facility, Monterey, Calif.
Advanced Water Purification Facility, Monterey, Calif.
Monterey One Water
A newly opened water treatment plant in Monterey, Calif., will replenish a vital regional groundwater resource with recycled water at a rate of millions of gallons per day. On an annual basis, the Pure Water Monterey treatment plant will inject at least 3,500 acre feet of water, equivalent to more than a billion gallons, into the Seaside Basin. 

For two decades, Monterey One Water, formerly the Monterey Regional Water Pollution Control Agency, has been recycling wastewater for irrigation in what’s called the “salad bowl of the world” where almost two-thirds of American leaf lettuce is grown. In addition to purifying wastewater, Pure Water is expanding to recycle agricultural drainage water, agricultural wash water and storm water runoff. 

“That’s a paradigm shift in thinking about recycled water,” said Paul Sciuto, the general manager of Monterey One Water. “The reason it’s so important is that communities can look around and find underutilized or unutilized water resources around them and then bring them into a system that can capture their benefits. “To my knowledge, it’s the first potable reuse plant in the country that uses all these source waters,” he added.

The launch of the project, the first of its kind in Northern California, is the culmination of years of cooperation by an unusually broad group of regional stakeholders. Pure Water Monterey was developed jointly by Monterey One Water, and the Monterey Peninsula Water Management District (MPWMD). Collaborators include the city of Salinas, the Marina Coast Water District, the Monterey Regional Waste Management District, the Fort Ord Reuse Authority, the city of Seaside, the Monterey County Water Resource Agency, the U.S. Bureau of Reclamation and the Monterey County Board of Supervisors.

“We really applaud inter-governmental cooperation to address these issues,” said Dennis Murphy, water director for Sustainable Silicon Valley, a nonprofit that brings tech companies, cities, counties, research and educational institutions together to solve sustainability problems. “They’re bigger than any one utility or treatment plan. They’re watershed-wide.”

Treating Before Recharging

Source water received by Monterey One Water goes through a four-step advanced treatment process before it is sent to recharge the aquifer. The first is the addition of ozone, which is more effective against bacteria and viruses than chlorination. Ozone also helps reduce concentrations of minerals associated with odor and taste problems.

The next stages involve membrane filtration and then reverse osmosis, a technique that is also used to process water for use in dialysis and drug manufacturing. In the final step, hydrogen peroxide is added to the water in the presence of UV light, to address any remaining traces of pollutants.

The wastewater sources includes raw sewage. Stanford researchers found that while most Californians approve of water recycling, only 11 percent would be willing to drink it. The great majority, more than three-fourths, would be also unwilling to bathe in it or cook with it. Reflecting these attitudes, some citizens raised concerns about the safety of what was being added to the water supply.

To help residents understand the process and assure them that the treated water is safe enough to be added to the drinking water supply, the utility created a demonstration facility. “The beauty of what we've done by having that demonstration facility is that seeing is believing,” said Mike McCullough, Monterey One Water’s director of external affairs. 

“We have the equipment on a much smaller scale and you can follow the water through the different processes,” he said. “At the end, you see what that water looks like after it goes through them, and we have water available if they’d like to try it. When you combine seeing the technology and discovering that what comes out is good-tasting water, it's a powerful story.”

Environmental Benefits

Prior to the existence of the Pure Water Monterey plant, agricultural and industrial drainage water, as well as contaminated stormwater, made its way into the local watershed. Capturing these waters and purifying them to potable standards has the added benefit of reducing the toxic burden on local ecosystems.

“There are two ditches or drains at the Salinas Valley,” said Sciuto. “One is Reclamation Ditch and one is Blanco drain. We are taking pollutant loads out of the environment off those two drains, bringing into our treating plant, treating the water and reusing it.”

Beyond this, recycling water reduces effluent from the treatment plant. “Our outfall happens to be in the Monterey Bay National Marine Sanctuary,” noted Sciuto. “If we can reduce the amount of treated effluent that goes out there, it's just better overall for the environment and this community as a whole.”

Recharging the aquifer is also a bulkhead against seawater incursion in the aquifer. “That's a constant fight in the area,” said Murphy. “If groundwater is depleted, seawater will fill the gap and basically spoil an important drinking water supply.” 

As an additional act of stewardship, Monterey One Water negotiated a power purchase agreement with the Monterey Regional Waste Management District (MRWMD) to secure renewable energy for the Pure Water Monterey facility. MRWMD’s anerobic digesters convert organic waste into biogas that is used to generate electricity. 


As water supplies from traditional sources decrease, more suppliers may need recycled or desalinated water to meet demand. (Billy Gadbury/Shutterstock)

Unlawful Water Diversion

As long ago as 1995, the California State Water Resources Control Board ruled that the local water purveyor, California American Water Company (Cal Am), was diverting substantial amounts of water from the Carmel River “without a valid basis of right.” The board ordered Cal Am to terminate this “unlawful diversion.” 

Illegal or not, Cal Am’s actions have had enough support from business and residential customers in a water-hungry community that the diversion has continued . An ongoing series of orders, hearings, public comment and reports have continued to address their practices, attempting to bring about significant reductions in the amount of diverted water. 

“Cal Am has a regulatory deadline of Dec. 31, 2021 to find additional water sources,” said Sciuto. “Our project coming online and producing about 3,500 to 3,700 acre-feet per year is necessary so we don't run into a regulatory buzz saw in another two years.”

The Cost of Recycling

The Pure Water Monterey project price tag was initially estimated at $113 million, but as work moved forward, the figure increased to $124 million. When operations and maintenance costs are factored in, the most recent estimate of the cost per acre-foot of water is $2,100 per acre-foot, higher than the $1,720 initially projected.

Even though this is 20 percent higher than the original estimate, it is within the cost range for water recycling projects. According to data collected by the California Public Utilities Commission (CPUC), recycled water averages $2,869 per acre-foot, less than the average cost of $3,389 for desalinated water. By comparison, the CPUC found that cost of water conservation in California could range from an average of $1,355 to as much as $4,580.

While the price for recycled water is greater than the average $793 per acre-foot for water from traditional sources in California, communities affected by drought and groundwater depletion may have few other options once conservation efforts reach their limits.

Other Aquifers Also Need Recharging

California is not the only part of the country where using recycled water to recharge aquifers could be not only smart but also necessary. The Ogallala aquifer, in America’s high plains, supports the cultivation of one-sixth of the world’s grain supply and provides one-third of the agricultural irrigation water used in the country.

Water levels in the aquifer are going down as much as two feet each year, but recharging from rain and snow melt averages around three inches. A paper published in the University of Denver Water Law Review points out that “long term unsustainable use of the aquifer is forcing states in the region to face the prospect of a regional economic disaster.”

Moreover, recent research suggests that, throughout the country, the available water resources in aquifers have been overestimated. Scientists from universities in Canada, Arizona and California concluded that the average depth at which fresh water in aquifers transitions to brackish (salty) water, which is unsuitable for drinking or agriculture, is about 1,800 feet. Previous studies had suggested the average depth was 6,500 feet.

Added to this are uncertainties about how climate warming will affect the rain and snow levels available to refill aquifers. “Weather patterns are changing all over the country,” said Adrienne Alvord, western states director for the Union of Concerned Scientists. “West of the hundredth parallel, when you hit the sort of mythical dry line in the center of the country, there are systems that collect water from snowfall and supply it in the hot, dry months. Increasingly, that's a problematic paradigm. It's not just California that's going to have to make adjustments. We're going to have to change our assumptions about what's going to be available and when, and how,” she said. “We're going to need to be very creative and flexible to respond to these changes if we're going to have sustainable water supplies.”

Water Reuse Central to Supply

Sustainable groundwater management will require more than reclaiming water that is being drawn out of aquifers, used, and then channeled out of the water supply. Even so, water recycling is likely to be essential for many jurisdictions.

“Water reuse has been thought of something almost on the side; nice to do, but just kind of experimental,” said Murphy. “But it’s very quickly becoming a central component of water supply.”

Pure Water Monterey is California’s newest exemplar of this trend and its potential. “I think this project can be replicated elsewhere and be a good model, frankly,” said Sciuto.

“The board of directors of this agency deserve a great deal of credit for saying, ‘We're going to spend some money and we're going to spend staff time to move this thing forward’,” he added.

“It's very easy for entities to say that something is outside of their scope,” said Sciuto. “We had visionary board members that allowed this project to move ahead, and the end result is you have the first potable reuse plant in Northern California.”

Carl Smith is a senior staff writer for Governing and covers a broad range of issues affecting states and localities. He can be reached at or on Twitter at @governingwriter.
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